Oil pipeline nonlinear fracture mechanics with through longitudinal cracks

UDK: 622.692.4.004.6:658
DOI: 0.24887/0028-2448-2021-10-122-126
Key words: main pipeline, durability, safety degree, linear breakdown mechanics, nonlinear breakdown mechanics, crack, stress intensity factors, deformation intensity factors, ductile fracture, brittle fracture
Authors: N.A. Mahutov (The Pipeline Transport Institute LLC, RF, Moscow), D.A. Neganov (The Pipeline Transport Institute LLC, RF, Moscow), E.P. Studenov (The Pipeline Transport Institute LLC, RF, Moscow), V.M. Varshickiy (The Pipeline Transport Institute LLC, RF, Moscow), A.S. Tusenkov (Ufa State Petroleum Technological University, RF, Ufa), S.A. Yamshikova (Ufa State Petroleum Technological University, RF, Ufa)

In domestic and international regulations the calculation of pipeline durability is performed based on force criterion under stress in form of allowed limit states and allowed limit stresses. This assumes that pipeline level of defect, at the point of its installation, construction and operation, remains within the norm of flaw detection control. However, continuous practice of pipelines operation (up to 40-50 years) demonstrates that these calculations do not exclude the appearance and development of flaw and cracks with sizes not only exceeding the norms, but also leading to loss of tightness and breakdown.

This article covers the analysis problems of the most dangerous states of main oil pipelines for transportation of oil and oil products in the event of longitudinal welded cracks, leading to loss of tightness and further breakdown. Normative methods of durability main calculations based on allowed loads, combined with methods of linear and nonlinear destruction mechanics were used as a basis for analysis. For modern pipelines, manufactured from enhanced plasticity pipe steel, reaching limit states within and outside of crack area happens upon occurrence of developed plastic regions, notably altering rated and local stress strain state. Taking this into account, the necessity and possibility of using a combination of force criterion of linear breakdown mechanics - critical coefficients of load intensity, critical coefficients of deformation intensity within the system of relative parameters was justified and proposed. This allows performing calculations for cases of high rated and local deformation, exceeding elasticity limits by tens and hundreds of times. Calculations show significant increase of limit crack size after transition from brittle to ductile fractures.

References

1. Mazur I.I., Ivantsov O.N., Bezopasnost' truboprovodnykh sistem (Pipeline safety), Moscow: Nedra Publ., 2004, 1099 p.

2. Radionova S.G., Zhulina S.A., Makhutov N.A. et al., Research prospects in the field of risk analysis for improvement of government regulation and safety increase of the oil and gas chemical complex objects (In Russ.), Bezopasnost' truda v promyshlennosti, 2017, no. 9, pp. 5–13.

3. Makhutov N.A., Deformatsionnye kriterii razrusheniya i raschet elementov konstruktsiy na prochnost' (Deformation criteria for fracture and strength analysis of structural elements), Moscow: Mashinostroenie Publ., 1981, 272 p.

4. Neyber G., Khan G., Problems of stress concentration in scientific research and technology (In Russ.), Mekhanika, 1967, no. 3, pp. 96–112.

5. Lisin Yu.V., Makhutov N.A., Neganov D.A. et al., Integral mechanical tests in the strength calculations of the main pipeline for transportation of oil and oil products (In Russ.), Zavodskaya laboratoriya. Diagnostika materialov, 2018, V. 84, no. 4, pp. 47–59.

6. Makhutov N.A., Prochnost' i bezopasnost': fundamental'nye i prikladnye issledovaniya (Strength and safety: fundamental and applied research), Novosibirsk: Nauka Publ., 2008, 528 p.

7. Lisin YU.V., Makhutov N.A., Neganov D.A., Varshitskiy V.M., Comprehensive analysis of the pipelines safety and basic mechanical properties of the pipe steels (In Russ.), Nauka i tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2017, no. 1(28), pp. 30–38.

8. Kiefner J.F., Failure stress levels of flaws in pressurized cylinders, American society of testing and materials report, 1973, ASTM STP 536, pp. 461–481.

9. Pluvinage G., Mécanique élastoplastique de la rupture: Critères d'amorçage, Cepadues, 1989.

10 . Matvienko Yu.G., Safety factors in structural integrity assessment of components with defects, International Journal of Structural Integrity, 2013, no. 4, pp. 457–476.

11. Bezopasnost' Rossii. Pravovye, sotsial'no-ekonomicheskie i nauchno-tekhnicheskie aspekty. Bezopasnost' sredstv khraneniya i transporta energoresursov (Security of Russia. Legal, socio-economic and scientific-technical aspects. Security of energy storage and transportation facilities): edited by Makhutov N.A., Moscow: Znanie Publ., 2019, 928 p.

12. Makhutov N.A., Permyakov V.N., Resurs bezopasnoy ekspluatatsii sosudov i truboprovodov (Resource of safe operation of vessels and pipelines), Novosibirsk: Nauka Publ., 2005, 516 p.

13. Makhutov N.A., Konstruktsionnaya prochnostʹ, resurs i tekhnogennaya bezopasnostʹ (Structural strength, life and man-made safety), Novosibirsk: Nauka Publ., 2005, Part 1, 494 p., Part 2, 610 p.

In domestic and international regulations the calculation of pipeline durability is performed based on force criterion under stress in form of allowed limit states and allowed limit stresses. This assumes that pipeline level of defect, at the point of its installation, construction and operation, remains within the norm of flaw detection control. However, continuous practice of pipelines operation (up to 40-50 years) demonstrates that these calculations do not exclude the appearance and development of flaw and cracks with sizes not only exceeding the norms, but also leading to loss of tightness and breakdown.

This article covers the analysis problems of the most dangerous states of main oil pipelines for transportation of oil and oil products in the event of longitudinal welded cracks, leading to loss of tightness and further breakdown. Normative methods of durability main calculations based on allowed loads, combined with methods of linear and nonlinear destruction mechanics were used as a basis for analysis. For modern pipelines, manufactured from enhanced plasticity pipe steel, reaching limit states within and outside of crack area happens upon occurrence of developed plastic regions, notably altering rated and local stress strain state. Taking this into account, the necessity and possibility of using a combination of force criterion of linear breakdown mechanics - critical coefficients of load intensity, critical coefficients of deformation intensity within the system of relative parameters was justified and proposed. This allows performing calculations for cases of high rated and local deformation, exceeding elasticity limits by tens and hundreds of times. Calculations show significant increase of limit crack size after transition from brittle to ductile fractures.

References

1. Mazur I.I., Ivantsov O.N., Bezopasnost' truboprovodnykh sistem (Pipeline safety), Moscow: Nedra Publ., 2004, 1099 p.

2. Radionova S.G., Zhulina S.A., Makhutov N.A. et al., Research prospects in the field of risk analysis for improvement of government regulation and safety increase of the oil and gas chemical complex objects (In Russ.), Bezopasnost' truda v promyshlennosti, 2017, no. 9, pp. 5–13.

3. Makhutov N.A., Deformatsionnye kriterii razrusheniya i raschet elementov konstruktsiy na prochnost' (Deformation criteria for fracture and strength analysis of structural elements), Moscow: Mashinostroenie Publ., 1981, 272 p.

4. Neyber G., Khan G., Problems of stress concentration in scientific research and technology (In Russ.), Mekhanika, 1967, no. 3, pp. 96–112.

5. Lisin Yu.V., Makhutov N.A., Neganov D.A. et al., Integral mechanical tests in the strength calculations of the main pipeline for transportation of oil and oil products (In Russ.), Zavodskaya laboratoriya. Diagnostika materialov, 2018, V. 84, no. 4, pp. 47–59.

6. Makhutov N.A., Prochnost' i bezopasnost': fundamental'nye i prikladnye issledovaniya (Strength and safety: fundamental and applied research), Novosibirsk: Nauka Publ., 2008, 528 p.

7. Lisin YU.V., Makhutov N.A., Neganov D.A., Varshitskiy V.M., Comprehensive analysis of the pipelines safety and basic mechanical properties of the pipe steels (In Russ.), Nauka i tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2017, no. 1(28), pp. 30–38.

8. Kiefner J.F., Failure stress levels of flaws in pressurized cylinders, American society of testing and materials report, 1973, ASTM STP 536, pp. 461–481.

9. Pluvinage G., Mécanique élastoplastique de la rupture: Critères d'amorçage, Cepadues, 1989.

10 . Matvienko Yu.G., Safety factors in structural integrity assessment of components with defects, International Journal of Structural Integrity, 2013, no. 4, pp. 457–476.

11. Bezopasnost' Rossii. Pravovye, sotsial'no-ekonomicheskie i nauchno-tekhnicheskie aspekty. Bezopasnost' sredstv khraneniya i transporta energoresursov (Security of Russia. Legal, socio-economic and scientific-technical aspects. Security of energy storage and transportation facilities): edited by Makhutov N.A., Moscow: Znanie Publ., 2019, 928 p.

12. Makhutov N.A., Permyakov V.N., Resurs bezopasnoy ekspluatatsii sosudov i truboprovodov (Resource of safe operation of vessels and pipelines), Novosibirsk: Nauka Publ., 2005, 516 p.

13. Makhutov N.A., Konstruktsionnaya prochnostʹ, resurs i tekhnogennaya bezopasnostʹ (Structural strength, life and man-made safety), Novosibirsk: Nauka Publ., 2005, Part 1, 494 p., Part 2, 610 p.


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